KR20060016251A - Liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device of the field sequential method.

According to the present invention, data to be currently displayed is stored in one of two memories using at least two memories, and after storing all the stored data, new data is stored in the one memory. In this way, a tearing effect that occurs when data to be displayed is updated to the next data can be prevented.

Liquid crystal display. Field Sequential Drive, Frame Memory, Field

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY DEVICE}

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is an equivalent circuit diagram of one pixel of a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a timing diagram illustrating an operation of a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a block diagram showing an internal configuration of a timing controller according to the first embodiment of the present invention.

5 is a block diagram showing an internal configuration of a timing controller according to a second embodiment of the present invention.

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device of a field sequential driving method.

Recently, display devices are also required to be lighter and thinner in accordance with the light weight and thickness of personal computers and televisions, and according to such demands, flat panels such as liquid crystal displays (LCDs) instead of cathode ray tubes (CRTs) are required. Display is being developed.

The liquid crystal display device applies an electric field to a liquid crystal material having an anisotropic dielectric constant injected between two substrates, and adjusts the intensity of the electric field to control the amount of light transmitted from the external light source (backlight) to the substrate. It is a display device which obtains a desired image signal.

Such a liquid crystal display is representative of a portable flat panel display, and among these, a TFT-LCD using a thin film transistor (TFT) as a switching element is mainly used.

In general, the liquid crystal display may be classified into two methods, a color filter method and a field sequential driving method, according to a method of displaying a color image.

A color filter type liquid crystal display device forms a color filter layer consisting of three primary colors of red (R), green (G), and blue (B) on one of two substrates, and adjusts the amount of light transmitted through the color filter layer. By doing so, a desired image is displayed. The color filter type LCD synthesizes R, G, and B colors by adjusting the amount of light transmitted through the R, G, and B color filter layers in transmitting light emitted from a single light source to the R, G, and B color filter layers. By doing so, a desired image is displayed.

As described above, in a liquid crystal display device displaying an image using a single light source and a three-color color filter layer, a corresponding unit pixel is required for each of the R, G, and B regions, and thus three times as many pixels as those for displaying black and white. Will be needed. Therefore, in order to obtain a high resolution image, sophisticated manufacturing technology of a liquid crystal display panel is required. In addition, such a liquid crystal display device has manufacturing difficulties in that a separate color filter layer is formed on a substrate, and the luminance is lowered because the light transmittance of the color filter itself is low.

The liquid crystal display of the field sequential driving method periodically turns on independent light sources of R, G, and B colors, and applies a color signal corresponding to each pixel in synchronization with the lighting cycle to generate a full color image. Get That is, according to the liquid crystal display of the field sequential driving method, R, G, and B primary colors output from R, G, and B backlights are output to one pixel without dividing one pixel into R, G, and B unit pixels. By displaying the light sequentially in time division, an image is displayed using the afterimage effect of the eye.

Such a field sequential driving method may be classified into an analog driving method and a digital driving method.

The analog driving method sets a plurality of gray voltages corresponding to the number of gray scales to be displayed, selects one gray voltage corresponding to gray data among the gray voltages, and drives the liquid crystal panel with the selected gray voltage to thereby apply the applied gray voltage. The gradation is indicated by the corresponding transmission amount.

On the other hand, in the digital driving method, the driving voltage applied to the liquid crystal is made constant, and the voltage application time is controlled to display the gray scale. According to this digital driving method, the gray scale is displayed by adjusting the accumulated amount of light transmitted through the liquid crystal by keeping the driving voltage constant and controlling the voltage applied state and the voltage unapplied state in a timely manner.

In such a liquid crystal display device, when a frame frequency displayed on an image and a frequency of input data are inconsistent with each other, a tearing effect in which two or more types of data (ie, two or more frames of data) are displayed on one screen. Phenomena occur. Due to such a tearing effect, two or more frames of data are divided and displayed on one screen in a color filter type liquid crystal display, and in a field sequential type liquid crystal display, specific R, G, and B colors are used as data of the next frame. It is updated to show a different color, so that a phenomenon such as point noise is observed.

In order to solve this problem, a color filter type liquid crystal display uses a method of changing the frame frequency displayed on the screen at the same speed as the frequency of the input data. However, when the frequency change method is applied to the liquid crystal display of the field sequential method, a problem occurs because it affects the gray scale. In the field sequential liquid crystal display, since a frame is driven by dividing one frame into an R field, a G field, and a B field, a frequency three times faster than that of the color filter method is required. This is because there is a problem with the expression.

SUMMARY OF THE INVENTION The present invention has been made in an effort to solve the above-described problems of the related art, and to provide a liquid crystal display device which prevents point noise caused by a tearing effect.

A liquid crystal display device according to a feature of the present invention for achieving the above object is

Matrix form having a plurality of scan lines for transmitting a scan signal, a plurality of data lines intersecting and intersecting the scan lines, a switching element formed in an area surrounded by the scan lines and data lines, and connected to the scan lines and data lines, respectively. A liquid crystal display panel including a plurality of pixels arranged in a line;

A light source sequentially outputting red, green, and blue light to one pixel;

A gray voltage generator which generates a gray voltage corresponding to gray data;

A data driver to output the gray voltage from the gray voltage generator to the data line; And

And a timing controller including first and second frame memories and controlling the first and second frame memories to transmit stored gray data to the gray voltage generator, and to control operations of the data driver and the light source. ,

 The timing controller causes the grayscale data to be displayed in the current frame to be stored in the first frame memory, and after the grayscale data stored in the first frame memory is output, the new grayscale data is stored in the first frame memory.

Here, the timing controller controls the next frame data to be stored in the second frame memory while the grayscale data stored in the first frame memory is output, and outputs all the grayscale data stored in the first frame memory. It is determined whether all of the next frame data is stored in the two frame memory, and when all are stored, the data stored in the second frame memory is output.

Plasma display device according to another aspect of the present invention

Matrix form having a plurality of scan lines for transmitting a scan signal, a plurality of data lines intersecting and intersecting the scan lines, a switching element formed in an area surrounded by the scan lines and data lines, and connected to the scan lines and data lines, respectively. A liquid crystal display panel including a plurality of pixels arranged in a line;

A light source sequentially outputting red, green, and blue light to one pixel;

A gray voltage generator which generates a gray voltage corresponding to gray data;

A data driver to output the gray voltage from the gray voltage generator to the data line; And

A first memory for storing frame data and a second memory for storing data corresponding to any one of the colors of red, green, and blue, and the grayscale data stored by controlling the first and second memories. A timing controller which transmits to a gray voltage generator and controls an operation of the data driver and the light source,

The timing controller is configured to store gradation data of a color to be currently displayed in the second memory, and to store gradation data of a next color into the second memory after the gradation data of a color stored in the second memory is output. . Herein, the capacity of the second memory is substantially 1/3 of the capacity of the first memory.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification.

A liquid crystal display and a driving method thereof according to an embodiment of the present invention will now be described in detail with reference to the drawings.

1 is a diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel of the liquid crystal display according to the exemplary embodiment of the present invention.

As shown in FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 100, a gate driver 200, a data driver 300, a gray voltage generator 400, and a timing controller 500. And light emitting diodes 600a, 600b, and 600c that output R, G, and B light, and a light source controller 700.

The liquid crystal display panel 100 includes a plurality of display signal lines S1 -Sn and D1 -Dm and a plurality of pixels 110 that are connected to the plurality of display signal lines S1-Sn and D1-Dm in an equivalent circuit.

The display signal lines S1 -Sn and D1 -Dm include a plurality of scan lines S1 -Sn for transmitting a gate signal (also referred to as a "scan signal") and data lines D1 -Dm for transmitting a data signal. The scan lines S1-Sn extend substantially in the row direction and are substantially parallel to each other, and the data lines D1-Dm extend substantially in the column direction and are substantially parallel to each other.

Each pixel includes a thin film transistor 10 connected to display signal lines S1 -Sn and D1 -Dm, a liquid crystal capacitor C1, and a storage capacitor Cst connected thereto. Holding capacitor Cst can be omitted as needed.

The thin film transistor 10 is a three-terminal element whose control terminal and input terminal are connected to the scanning line S1-Sn and the data line D1-Dm, respectively, and the output terminal is the liquid crystal capacitor C1 and the storage capacitor Cst. )

The liquid crystal capacitor C1 has a pixel electrode (not shown) and a common electrode (not shown) as two terminals, and the liquid crystal layer between the two electrodes functions as a dielectric. The pixel electrode is connected to the thin film transistor 10 and the common electrode receives a common voltage Vcom.

The storage capacitor Cst is formed by overlapping a separate signal line (not shown) and the pixel electrode, and a predetermined voltage such as the common voltage Vcom is applied to the separate signal line.

In FIG. 2, when the scan signal is applied to the scan line Si and the thin film transistor 10 is turned on, the data voltage Vd supplied to the data line is applied to each pixel electrode through the thin film transistor 10. Then, an electric field corresponding to the difference between the pixel voltage Vp and the common voltage Vcom applied to the pixel electrode is applied to the liquid crystal (equivalently represented by the liquid crystal capacitor in FIG. 2), and thus transmittance corresponding to the intensity of the electric field. To allow light to pass through. At this time, the pixel voltage Vp should be maintained for one frame or one field, and the storage capacitor Cst is used to maintain the pixel voltage Vp applied to the pixel electrode.

Referring back to FIG. 1, the gate driver 200 sequentially applies a scan signal to the scan lines S1 -Sn, thereby turning on the thin film transistor having the gate electrode connected to the scan line to which the scan signal is applied.

The gray voltage generator 400 generates a gray voltage having a magnitude corresponding to gray data and supplies it to the data driver 300. The data driver 300 applies the gray voltage output by the gray voltage generator 400 to the corresponding data line.

The timing controller 600 is a horizontal synchronization with an input control signal for controlling the RGB image signals R, G, and B data and their display from an external graphic controller (not shown), for example, a vertical synchronization signal Vsync. Receive a signal (Hysnc) and the like. The timing controller 400 properly processes the image signals R, G, and B according to the operating conditions of the liquid crystal display panel 100 based on the input image signals R, G, and B and the input control signal, and controls the gate control signal. After generating Sg, the data control signal Sd, the light source control signal Sb, and the like, the gate control signal Sg is sent to the gate driver 200 and the data control signal Sd is sent to the data driver 300. The processed image signals R, G, and B DATA are sent to the gray voltage generator 500 and the light source control signal Sb is sent to the light source controller 700. Here, the timing controller 600 according to an embodiment of the present invention includes two memories to properly process the input image signals R, G, and B, and frame data is read while reading one frame of data from the memory. This prevents the tearing effect caused by the update.

The light emitting diodes 600a, 600b, and 600c respectively output light corresponding to R, G, and B to the liquid crystal display panel 100, and the light source controller 700 determines when the light emitting diodes 600a, 600b, and 600c are turned on. To control. In this case, according to an exemplary embodiment of the present invention, the timing controller 500 may be configured to supply the grayscale data from the data driver 300 to the data line and to turn on the R, G, and B light emitting diodes by the light source controller 700. It can be synchronized by the control signal provided by.

Next, the display operation of the liquid crystal display will be described in detail with reference to FIG. 3.

3 is a timing diagram illustrating an operation of a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 3, the liquid crystal display according to the exemplary embodiment of the present invention displays an image by dividing one frame into three fields, that is, an R field, a G field, and a B field. If the drive frequency of one frame is 60 Hz, each field performs display operation in synchronization with 180 Hz. Here, G1, G2, ... Gn represent a scanning signal applied to each gate line, and Cr, Cg, Cb represent a lighting signal for instructing the lighting of R, G, and B light emitting diodes 600a, 600b, and 600c. Indicates.

One frame of R, G, and B image data supplied from the outside is separated into one frame of R image data, G image data, and B image data by the timing controller 400 to match the display operation of the liquid crystal display device. Are converted and stored in frame memory (which may be contained within a timing controller). The stored image data of each raw image reads R image data in an R field period of 1/180 sec divided into three frames in accordance with a read signal from the timing controller 400, followed by G image data in the G field. Subsequently, B image data is sequentially read into the B field.

In the R field, the R image data voltage is sequentially written to all the pixels according to the scan signals G1, G2, ... Gn, and then the light emitting diode 600a is turned on according to the lighting signal Cr in the illumination period. The R image is displayed on the liquid crystal display panel 100.

The G image data voltage is sequentially written to all the pixels according to the scan signals G1, G2, ..., Gn in the writing section of the G field, and then the light emitting diode 600b lights up in accordance with the lighting signal Cg in the lighting section. The G image is displayed on the liquid crystal display panel 100.

The B image data voltage is sequentially written to all the pixels according to the scan signals G1, G2, ..., Gn in the writing section of the B field, and then the light emitting diode 600c lights up in accordance with the lighting signal Cb in the lighting section. The B image is displayed on the liquid crystal display panel 100.

In this way, the image corresponding to each color component of R, G, and B is sequentially displayed for each field of each color of the R, G, and B fields so that the image of the R, G, and B color components is a visual afterimage of human. Is synthesized and visually recognized as a color image of one frame.

In FIG. 3, each field is divided into a writing period and an illumination period to display an image. However, the present invention is not limited thereto, and a reset period for erasing the data voltage applied in the previous field may be separately included.

Hereinafter, a configuration of a memory for storing R, G, and B data input to solve a tearing effect problem in the above liquid crystal display will be described. In the embodiments of the present invention described below, a memory for storing R, G, and B data is described as being included in the timing controller 400. However, the present invention is not limited thereto, and the memory is a data driver 300. It can be installed in or separately.

4 is a block diagram showing an internal configuration of a timing controller according to the first embodiment of the present invention. 4 shows only an internal configuration for storing and outputting R, G, and B data in an internal memory of the timing controller, and the rest of the configuration is omitted for convenience.

As shown in FIG. 4, the timing controller according to the first embodiment of the present invention includes a first switch 410, a second switch 440, a first frame memory 420, and a second frame memory 430. And a controller 450.

The first switching unit 410 switches to store the input R, G, and B data in the first frame memory 420 or the second frame memory 430 according to the control signal of the controller 450. do. Meanwhile, the second switching unit 410 switches to output data stored in the first frame memory 420 or data stored in the second frame memory 430 according to the control signal of the controller 450.

In the first and second frame memories 420 and 430, R, G, and B data of one frame are separately stored and written or read, respectively. Here, if the frame data (N-th frame data) to be output to the current frame (N-th frame) is stored and output in the first frame memory 420, the next frame (N) is simultaneously stored in the second frame memory 430. The frame data (N + 1st frame data) to be output is stored in the + 1st frame. Next, when the N + 1 th frame data stored in the second frame memory 430 is output in the N + 1 th frame, the N + second frame data is stored in the first frame memory 420 at the same time. do. In this case, the gray scale data output from the first frame memory 420 or the second frame memory 430 is transmitted to the gray voltage generator 500.

The controller 450 generates a control signal for controlling the first switch 410 and the second switch 440. The controller 450 outputs the data stored in the frame memory of one of the first and second frame memories 420 and 430, and stores the next frame data in the other memory. Generates a control signal to provide to the first switching unit 410 and the second switching unit 440. That is, the controller 450 controls the second switching unit 440 to output the N-th frame data stored in the first frame memory 420 and the N + 1-th frame data is stored in the second frame memory 430. The first switching unit 410 is controlled to store in the. In this case, when the stored frequency is slower than the output frequency, the controller 450 may prevent the Nth frame stored in the first frame memory 420 in order to prevent the data from being output before the data is stored in the frame memory. After outputting up to the data of the last scan line of the data, it is checked whether the storage is completed in the second frame memory 430 and controls to output the frame data stored in the second frame memory 430 when the storage is completed. Meanwhile, after all data stored in the first frame memory 420 is output, the controller 450 controls the first switching unit 410 to store the N + 2th frame data in the first frame memory 420. do.

According to the timing controller according to the first embodiment of the present invention, since the N + 1th frame data is stored in another frame memory while the Nth frame data is read, the Nth frame is read and displayed on the LCD panel. The tearing effect problem caused by updating the + 1th frame data can be prevented.

However, in the first embodiment of the present invention, since two frame memories are used, a problem arises in that a large memory capacity is required. As described in FIG. 3, the liquid crystal display according to the exemplary embodiment of the present invention is driven by dividing one frame into an R field, a G field, and a B field, and thus does not use two frame memories as in the timing controller of the first embodiment. It can be used as a memory corresponding to one frame memory and one-third of the frame memory.

5 is a block diagram showing an internal configuration of a timing controller according to a second embodiment of the present invention. In FIG. 5, only an internal configuration for storing and outputting R, G, and B data in an internal memory of the timing controller is illustrated. Other configurations are omitted for convenience.

As shown in FIG. 5, the timing controller according to the second embodiment of the present invention includes a frame memory 420 ′, a one-color memory 430 ′, and a controller 450 ′. Here, the one color memory 430 ′ is a memory having a capacity corresponding to 1/3 of the frame memory 420 ′ and stores only data corresponding to one color of R, G, and B colors.

The frame memory 420 'stores R, G, and B data corresponding to one frame. The color memory 430 'is transmitted with the color data to be displayed in the current field (meaning one of the R, G, and B fields) from the frame memory 420'. For example, to output data corresponding to the R field of the Nth frame, the R, G, and B data of the Nth frame are stored in the frame memory 420 ', and the one color memory 430' is a frame. After receiving and storing R data from the memory 420 ', the R data is output. At this time, only after the R data stored in the one-color memory 430 'is output in the R field, the B-data period is transferred from the frame memory 420' to the one-color memory 430 'and stored. Is output from

The controller 450 ′ generates a control signal for controlling the frame memory 420 ′ and the one-color memory 430 ′. The controller 450 ′ transmits one color data among the R, G, and B data stored in the frame memory 420 ′ to the one color memory 430 ′, and is stored in the one color memory 430 ′. Before all data of one color is outputted, the data is controlled from the frame memory 420 'to the one color memory 430'.

Therefore, according to the second embodiment of the present invention, data to be displayed in the current field (one of the R, G, and B fields) is stored and output in one color memory, so that the next frame data is newly updated in the frame memory. Even if the data of the current field is not changed, the tearing effect problem can be prevented.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

As described above, according to the present invention, a separate memory may be added to store data to be displayed, thereby preventing a tearing effect problem caused by updating of data to be displayed.

Claims (8)

Matrix form having a plurality of scan lines for transmitting a scan signal, a plurality of data lines intersecting and intersecting the scan lines, a switching element formed in an area surrounded by the scan lines and data lines, and connected to the scan lines and data lines, respectively. A liquid crystal display panel including a plurality of pixels arranged in a line; A light source sequentially outputting red, green, and blue light to one pixel; A gray voltage generator which generates a gray voltage corresponding to gray data; A data driver to output the gray voltage from the gray voltage generator to the data line; And And a timing controller including first and second frame memories and controlling the first and second frame memories to transmit stored gray data to the gray voltage generator, and to control operations of the data driver and the light source. ,  The timing controller is configured to store the grayscale data to be displayed in the current frame in the first frame memory, and to allow the new grayscale data to be stored in the first frame memory after all the grayscale data stored in the first frame memory are output. Display device. The method of claim 1, And the timing controller controls the next frame data to be stored in the second frame memory while the grayscale data stored in the first frame memory is output. The method of claim 2, The timing controller outputs all the grayscale data stored in the first frame memory and then determines whether all the next frame data is stored in the second frame memory, and outputs the data stored in the second frame memory when all of the next frame data is stored. Display device. The method according to any one of claims 1 to 3, The timing controller A first switching unit which switches to selectively store the input gray level data in the first frame memory or the second frame memory; A second switching unit for switching to selectively output grayscale data stored in the first frame memory or the second frame memory; And a control unit for controlling switching of the first and second switching units. Matrix form having a plurality of scan lines for transmitting a scan signal, a plurality of data lines intersecting and intersecting the scan lines, a switching element formed in an area surrounded by the scan lines and data lines, and connected to the scan lines and data lines, respectively. A liquid crystal display panel including a plurality of pixels arranged in a line; A light source sequentially outputting red, green, and blue light to one pixel; A gray voltage generator which generates a gray voltage corresponding to gray data; A data driver to output the gray voltage from the gray voltage generator to the data line; And A first memory for storing frame data and a second memory for storing data corresponding to any one of the colors of red, green, and blue, and the grayscale data stored by controlling the first and second memories. A timing controller which transmits to a gray voltage generator and controls an operation of the data driver and the light source, The timing controller is configured to store gradation data of a color to be currently displayed in the second memory, and to store gradation data of a next color into the second memory after the gradation data of a color stored in the second memory is output. Liquid crystal display. The method of claim 5, The capacity of the second memory is substantially one third of the capacity of the first memory. The method according to claim 5 or 6, The data stored in the second memory is transmitted from the first memory. The method according to claim 5 or 6, The timing controller may further include a controller configured to control data storage and output of data in the first memory and the second memory.

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